* armos.c (ARMul_OSHandleSWI::SWI_Open): Handle special case
of ":tt" to catch stdin in addition to stdout.
(ARMul_OSHandleSWI::SWI_Seek): Return 0 or 1 to indicate failure
or success of lseek().
From PR 15839, modified a bit by me to appease my sense of style--but
not too much because I am lazy.
7d449b448b